This invention relates to impellers for centrifugal pumps of the type used to convey liquids. More particularly, it relates to straight-vaned impellers, commonly called radial impellers, and also to Francis-type impellers, commonly called semi-axial impellers.
In high energy pump impellers, cavitation can develop along impeller blades and adjacent surfaces in the following locations:
a. along the impeller blade surface;
b. near the intersection of the impeller blade with the hub surface; and
c. at the nose of the leading edge of the impeller blade. Such cavitation can cause rapid erosion of impeller blades at these locations, leading to early failure of the impeller or increased need for repairs.
An approach to combat this cavitation problem consists of modifying the curvature of each impeller vane on the suction side, in the area of the leading edge of the vane. However, this teaching deals with cavitation along the sides surfaces of impeller vanes, but does not address the cavitation at the other above-specified locations. There is a need, therefore, for an improved impeller that inhibits cavitation along the impeller blade surface, near the intersection of the impeller blade with the hub surface and at the nose of the leading edge of the impeller blade.
The foregoing illustrates limitations known to exist in present impellers. Thus it is apparent that it would be advantageous to provide an alternative directed to overcoming one or more of the limitations set forth above. Accordingly, a suitable alternative is provided including features more fully disclosed hereinafter.